A conventional J-pole antenna is an omnidirectional antenna that can be used for base, mobile and field day stations. It does not need a ground plane, radials or a complicated matching system.
A Conventional J-Pole design illustrated in FIG. 1. The J-Pole antenna 100 includes of a radiating antenna segment 101 and a quarter-wave matching segment 102. A feed line 103 connects to the radiating antenna segment. The matching segment 104 is connected to ground. The connection points on the J-Pole antenna between the feed line and ground are chosen to provide sufficient resistance to prevent shorting between the feed line and the ground. In a conventional J-Pole antenna, the shunt segment 105 is formed to extend down below to connection points. Typically, the length A of the radiating antenna segment 101 is ½ the wavelength of the frequency the antenna is designed to operate at. Typically, the length B of the matching segment 102 is ¼ the wavelength the antenna is designed to operate at.
Conventional J-pole antennas are made of a conductive tubing, such as copper or aluminum. There are versions made of 300-ohm TV twin lead, which can be rolled up easily into a small package.